Laterite nickel ore can be divided into two types according to its distribution and utilization properties, namely "dry type" and "wet type". In general, "dry" laterite weaker than the "wet" nickel laterite weathering, relatively more clay-containing composition, less composition goethite. The "wet type" laterite nickel ore contains less clay and is serpentine. The performance of the two types of laterite nickel ore is different. The high-pressure acid leaching (PHAL) process for the commercial application of laterite minerals began in the late 1950s, but it was not until the late 1990s that new plant inputs began, due to limitations in autoclave technology and solution processing technology. In recent years, the construction of new plants has also adopted high-pressure acid leaching. However, due to the different types and utilization properties of laterite nickel ore, and the situation in different places, especially in arid areas lacking fresh water, process water generally uses groundwater. The groundwater contains a large amount of Na + , Mg + , SO 2 4 , CL - plasma, which has a great influence on the leaching chemical reaction. Therefore, foreign researchers have conducted a series of studies on the effects of water salinity and mineral type. Whittington and Johnson believe that when seawater is used instead of freshwater to leach laterite nickel ore, the nickel leaching rate increases when the free acid concentration is higher. However, when the sodium ion concentration exceeds 15 g/L, the nickel leaching rate decreases and the leaching time increases. Whittington conducted high-pressure acid leaching studies on different laterite nickel ore types, and investigated the effects of mineral types on slag phase composition, iron, magnesium , and aluminum- nickel leaching. However, the above high-pressure acid leaching study of laterite nickel ore, the leaching temperature is 250-280 ° C, at this temperature, the pressure is higher, the requirements of the autoclave are higher, there is a safety hazard, which is not widely used in the high-pressure acid leaching process. The reason, so we propose an oxygen pressure acid leaching process for the Australian “dry†laterite nickel ore, that is, a certain amount of oxygen is initially charged in the reaction. The laterite ore can be leached at a lower temperature without reducing the leaching rate of nickel and cobalt . First, the experimental part (1) Ore characteristics and phase composition The stone used in the experiment is from Australia, ore composition (%): quartz and feldspar 26.99, montmorillonite and talc 19.24, hematite 17.32, humus-like brown ore 11.69, dense limonite 5.20 and maghemite magnetite 5.69, 4.82 clays, calcite and dolomite 3.33, 0.25 chromite, pyrrhotite trace, manganese 0.8 bauxite, iron-stained clay 2.3, 0.27 mica and illite, chlorite 2.1, ore major cost ( %): Ni l.07, CoO.1, Fe20.43, Mg2.48, Ca0.35, Si 20.57, Al 0.11, Mn0.4. It can be seen that the minerals in the stone are mainly gangue minerals such as stone, montmorillonite and talc, followed by limonite (a considerable part of the surface humus-like limonite), which indicates the ore system. "Dry" laterite nickel ore. (2) Test plan The leaching experiment was carried out in a 2L titanium autoclave. The temperature was automatically controlled by PID. The temperature control range was ±2 °C. It was electrically heated, built-in water cooling system and magnetic stirring. Analytical pure sulfuric acid was used as the leaching agent, and 100 g (-0.074 mm) of the ore sample was taken in each experiment, the liquid-solid ratio was 8:1, and the stirring speed was 300 r/min. The effects of sulfuric acid dosage, leaching time, leaching temperature and oxygen partial pressure on nickel, cobalt, iron leaching rate and free acid content were studied. Second, the results and discussion (1) The effect of sulfuric acid dosage The reaction temperature of sulfuric acid was 200 ° C, and the initial reaction was filled with oxygen at a pressure of 1 MPa, and the reaction time was 2 h. The results are shown in Fig. 1. It can be seen that when the amount of sulfuric acid is less than 30 mL, the leaching rate of nickel and cobalt does not change much, and is less than 90%. When the amount of sulfuric acid is more than 30mL, the leaching rate of nickel and cobalt increases obviously. When the amount of sulfuric acid is 40mL, the leaching rates of nickel and cobalt are 97.06% and 90.26%, respectively. With the increase of the amount of sulfuric acid, the leaching rate of iron increases, and the free acid content in the system also increases. Figure 1 Effect of sulfuric acid dosage Fig.1 Effect of sulfuric acid dosage on leaching rate (two) the effect of reaction temperature The amount of fixed sulfuric acid was 25 mL, and the reaction was initially filled with 0.5 MPa of oxygen (no oxygen at 250 ° C), and the reaction time was 2 h. The results are shown in Fig. 2. It can be seen from Fig. 2 that the leaching rate of nickel and cobalt increases as the temperature increases. However, the leaching rate of iron and iron does not change much, and the free acid content in the system decreases as the reaction temperature increases. The leaching rates of nickel and cobalt at 220 ° C and 5 MPa oxygen are 99.83% and 90.44%, respectively, while the iron leaching rate is only 2%, which basically enters the slag. The content in the solution is only 0.3 g/L, and 250 ° C, The leaching rates of nickel and cobalt when filled with oxygen are roughly equivalent. This indicates that the initial filling of a certain amount of oxygen can accelerate the reaction process and is beneficial to increase the leaching rate of nickel and cobalt. Figure 2 Effect of leaching temperature Fig.2 Effect of temperature on leaching rate (3) The impact of reaction time The fixed reaction temperature was 200 ° C, the reaction was initially filled with 0.5 MPa of oxygen, and the amount of sulfuric acid was 40 mL. The results are shown in Figure 3. It can be seen that the leaching rate of nickel and cobalt increases with the prolongation of reaction time, and prolonging the reaction time is beneficial to reduce the content of iron and free acid in the solution, which is convenient for subsequent treatment. Therefore, the suitable reaction time is 2h, and the leaching rates of nickel and cobalt are 97.06% and 90.26%, respectively. Figure 3 Effect of leaching time Fig.3 Effect of time on leaching rate (4) The effect of initial oxygen partial pressure The fixed reaction temperature was 200 ° C, the reaction time was 2 h, and the amount of sulfuric acid was 30 mL. The results are shown in Figure 4. As can be seen from Fig. 4, the initial oxygenation in the reaction is very effective in increasing the leaching rate of nickel and cobalt, but when the initial oxygen pressure is greater than 0.5 MPa, the effect is not obvious. Therefore, the suitable initial partial pressure of oxygen is 0.5 MPa. Figure 4 Effect of initial oxygen partial pressure Fig. 4 Effect of initial partial pressure ofoxygen on leaching rate (5) Exploration of reaction mechanism It was found that when a certain amount of oxygen was introduced into the reaction, the leaching rate of nickel and cobalt could be increased, and obvious oxygen consumption was observed during the reaction, indicating that oxygen is present in the ore. This indicates that the ore contains 11.69% of humus-like limonite, and a considerable part of the iron in the humus is in the form of ferrous iron. Therefore, when high-pressure acid leaching laterite ore, the first is the dissolution of ferrous iron, followed by the dissolution of magnesium, and then the oxidation of ferrous iron into ferric iron. The ferric acid releases acid to form two precipitates: iron hydroxysulfate precipitate (FeOHSO 4 ) and hematite precipitate. The iron hydroxysulfate precipitate is easy to form but unstable, and is quickly converted into hematite precipitate. The iron in the limonite is mainly in the form of goethite (α-FeOOH), and in the process of high-pressure acid, the ferric iron is dissolved after being dissolved. The dissolution of nickel is carried out in a poor manner in which nickel oxide is dissolved. Therefore, the reaction initially passes a certain amount of oxygen to facilitate the oxidation of the ferrous iron, accelerates the reaction, and makes the thermodynamic driving force of the reaction system become larger, so that the nickel-cobalt leaching rate is also higher at a lower temperature. The entire reaction process is as shown in equations (1) to (6): (1~6) formula Third, the conclusion The Australian "dry" laterite nickel ore is leached by an oxygen pressure acid leaching process. When the reaction initially introduces a certain amount of oxygen, the reaction process can be accelerated and the leaching rate of nickel and cobalt can be increased. Under the same conditions, the leaching rates of nickel and cobalt when the reaction was initially filled with 0.5 MPa of oxygen were 99.83% and 90.44%, respectively, while the iron leaching rate was only 2%, which basically entered the slag, and when it was not filled with oxygen at 250 °C. The nickel and cobalt leaching rates are roughly equivalent. Mahle Filters,Industrial Mahle Filters,Mahle Filter Element,Mahle Replacement Filter Henan Sinofiltec Technology Co.,Ltd , https://www.airfilters.pl