Taylor et al. was the earliest research and proposed formula for heap leaching rate in history. In 1942, they summed up the view of the river Spain Rio Ting Huang copper ore heap leaching production practice after the data, history presents a heap leaching rate equation, namely W i =1-exp(-kt)=1-e - kt (1) Wherein, W i - when time t, the amount of metal leached gold; K-heap leaching rate constant; T-leaching time. It is not difficult to see that here, Taylor et al. treat the total metal amount W 0 in the ore (heap) as 1. In fact, W i is only part of W 0 , and it is more intuitive to use fractions or percentages. It is also convenient when drawing. Let f r be the fraction of the amount of metal that has not been leached, ie f r = W r /W 0 . f i is the fraction of the amount of metal that has been leached, f i =W i /W 0 , then f r =1-f i =e - kt (2) If the two sides of the formula (2) are logarithm, then Ln(1-f i )=lne kt (3) For the formula (3), then The production data collected by Taylor et al. is plotted as shown in Figure 1 according to equation (4). In the figure, k is the heap leaching rate constant. The ordinate (1-f i) Not showing the amount of metal leaching (W r) of the total amount of metal (W 0) ore (heap) the fraction or percentage. Another equivalent expression (5) of the formula (1) can be derived from FIG. 1 and formula (2). Figure 3-4 Taylor-Vylan curve W r =(1-f i )= W r =e - kt W i =W 0 (1-e - kt ) (5) Taylor-Vylan's expressions, and the curves they plot, do not reflect the relationship between the parameters of the heap leaching process, such as ore particle size, heap height, leaching agent concentration, spray intensity, etc., and heap leaching rate constants. It is not related to the parameters of unsaturated flow, such as saturation, porosity, etc., and even the relationship between the metal concentration and the volume of the leachate commonly used in heap leaching is not directly related, so it is not convenient to use. In fact, the relationship between metal concentration versus time is commonly used to indicate the dynamics of the leaching process. As shown in equation (6): C= Equation (6) is quite straightforward, including the operating parameters in the heap leaching, W 0 is the total amount of metal in the heap (or test column), Q is the spray intensity used in the production or test, and S is the total heap The area, C is the concentration of metal ions in the leachate measured during production or testing, and t is the leaching time, so the k value is easily obtained. It can be known from formula (6) that during the heap leaching process, the metal concentration C in the leachate decreases with time, which is proportional to the total metal amount (W 0 ) in the ore (heap), and the amount of metal per unit area ( W 0 /S) is proportional, or when the ore grade is constant, the metal concentration in the leaching slag is proportional to the stack height and inversely proportional to the spray strength. In the actual process of heap leaching, on the graph of concentration versus time, as shown in Figure 2, there must be a maximum concentration value. Generally speaking, the concentration at this time is the peak concentration, which is represented by C p . When the time corresponding to C p is recorded as t p , t p , the metal concentration in the leachate gradually decreases until the metal concentration is low enough that the leaching is no longer economical. The concentration at this time is called the minimum economic concentration. Expressed in C mn . C p , C mn together with the average concentration C mv are important technical and economic parameters for evaluating heap leaching engineering. Figure 2 Relationship between uranium content and leaching time in solution 1- silicon diorite - porphyry; 2- granite; 3- clay slate; 4-ç²—é¢è‹±å®‰å²©;5- basalt Agricultural Wheel ,Agricultural Wheel Rims,Farm Wheel,Tractor Tires And Rims JIANGSU DONGZHIBAO AUTOMOBILE CO.,LTD , https://www.dzbwheels.com
(4) =e - kt e - kt (6)