Inputs for ore selection in Ansteel Dagushan and other concentrators (2)

Dong’anshan Mineral Processing Plant conducted a test to improve the concentrate grade in the No. 7 system from March 22 to March 29, 1978. According to the test results, when the output is basically unchanged when the ball mill, Figure 3, the relationship between the tailings is as follows with the change of the fine ore product position: θ = 993.987-31.721 station When the concentrate grade changes below 63%, the tailings grade will increase slightly; but when the concentrate grade exceeds 63%, the tailings grade will increase significantly.

Based on the product quality situation of Jiugang Mineral Processing Plant in 1979, nearly 3,000 data of 939 classes were collected from the dispatch daily report. The image of the data is shown in Figure 4. The equation is: y=2.78-1.66×1+0.148×2 (5) Jiugang’s 1979 data shows that the metal recovery rate increases with the increase of raw ore grade; improve by improving. This shows that the depth of mineral processing was not enough under the conditions at that time. With the fine grinding and deep separation of the ore, the minerals and gangue can be better separated, which not only improves the grade of the concentrate, but also achieves the purpose of increasing the recovery rate of the mineral processing. For the vast majority of domestic mineral cnc machining plants, as the concentrate grade increases, the metal recovery rate will be affected to a certain extent. Especially when the process remains unchanged and the ore is over-grinded, simply pursuing high grade will have a greater impact on the recovery rate. Figure 4.
[next] 2. The impact of increasing concentrate grade on the working capacity of the ball mill in the ore concentrator. The mill capacity is reduced. On the one hand, the concentrate output is reduced and the cost of the concentrate is increased. On the other hand, the concentrator needs to be expanded to make up for the loss of capacity. Each ton of product Occupying investment increases. Therefore, the mill capacity index is one of the important indicators that affects the investment effect of the mineral processing plant. The change of the ball mill capacity of each factory with the grade of mineral processing is closely related to the properties of the ore and the means of improving the grade of the concentrate. When the mineral processing process is basically fixed, the ore has been ground to a certain particle size, and then the concentrate grade is improved by fine grinding, the ball mill’s capacity will inevitably decrease. If the grade is improved on the basis of continuous improvement and improvement of the process flow, the ball mill’s capacity may not be reduced, or even improved to varying degrees. Before the Nanfen mineral processing plant adopted fine screening, it mainly relied on reducing the grinding particle size to improve the quality of iron concentrate. However, due to the different properties of ores, the grindability of ores varies greatly. Although under the same grinding particle size, the monomer dissociation degrees of useful minerals and gangue minerals are also different, and only most of the mineral monomers can be dissociated. Therefore, it is inevitable that a small amount of conjoined and over-crushed minerals will exist in the grinding products, which affects the improvement of the concentrate grade. In order to obtain high-grade concentrate, it is necessary to reduce the mill capacity, improve the grinding particle size, reduce the number of conjoined bodies, and fully dissociate useful minerals and gangue. The higher the requirements for concentrate grade, the finer the grinding particle size requirements, and the more serious the over-grinding phenomenon. For example, the concentrate grade increased from 65.13% from July to December 1976 to 66.35% from July 1977 to June 1978, and the ball mill advantages of high speed milling centers capacity dropped from 62.48t/(unit·h) to 53.40t/(unit·h) ), dropped by 9.08t/(unit·h). Figure 5.

In July, November 1978 and May 1979, the fine screen self-circulating regrinding process was realized in the third, fourth and second selection workshops respectively. A second-stage fine screen was installed with a mesh opening of 0.2mm and an inclination angle of 56°. The modification cost was 800,000. Yuan. The situation is very different after the vibrating fine screen is put into production. The fine screen separates iron concentrates smaller than the separation particle size as early as possible, and the particles with large dry separation particle size and their contiguous bodies become the products on the screen for re-grinding and re-selection, thus avoiding and reducing the phenomenon of magnetite concentrate over-grinding and shortening the grinding time. time, improving mill capacity. [next] From 1977 to the first quarter of 1981, the ball mill capacity of the ball mill changed with the concentrate grade. Based on this, a regression analysis was performed. Their relationship formula is: y=325.66-3.78x (6 ) (where y represents The ball mill’s hourly capacity, x represents the concentrate grade) That is, if the concentrate grade increases by 1%, the ball mill’s hourly capacity decreases by 3.78t. The statistical results are shown in Figure 6.

After the fine screening and regrinding workshop of the Dagushan Concentrator was put into operation, the ball mill capacity when the concentrate grade was 66% basically remained at the level of the original process. But when the concentrate grade increases further, the mill capacity decreases. When the concentrate grade reaches 67%, the mill capacity drops even more, from about 30t/(unit·h) to 26t/(unit·h). .The mill capacity changes of the mill based on the indicators from May 1978 to March 1979 are calculated according to different grades.

(3) Increase in concentrate cost The concentrate cost includes raw material fees and processing fees. As the grade of ore selection increases, both raw material fees and processing fees will increase. Raw material fee refers to the cost of raw ore that needs to be processed to produce each ton of concentrate. Even if other separation indicators are not affected, as the grade of concentrate increases and the yield decreases, the amount of raw ore per ton of concentrate increases, so the raw material cost Increase. The higher the mining cost of raw ore, the greater the impact on mineral processing. When the concentrate grade increases and the mineral processing metal recovery rate decreases, the increase in raw material costs will be greater. Therefore, the extent to which raw material costs increase as the concentrate grade increases depends not only on the changes in concentrate grade, recovery rate and other indicators in the concentrator, but also on the cost of mining raw ore in the mine. The processing costs of iron ore concentrate include steel balls, linings, water, electricity and other material consumption and power consumption, depreciation, repair and maintenance fees of fixed assets, wages and surcharges of production workers, workshop expenses and corporate management fees wait. Changes in these costs can be obviously reflected when the process flow of the mineral processing plant undergoes major changes, but in daily production, when the process and equipment basically remain unchanged, but some individual separation indicators change within a limited range, they will not be reflected. It’s obvious. In particular, due to frequent changes in the prices of various consumable materials and inaccurate measurement of various on-site consumption quotas, the relationship between changes in financial statements and technical and economic indicators is not strong. However, whether it is easy-to-select ore or difficult-to-select ore, no matter what method is used to improve the concentrate grade, the processing cost will always increase with the increase in concentrate grade. The impact of ore beneficiation on ore beneficiation processing costs can be calculated by the following method. A. Quota Calculation Method This method is applicable when there are major changes in the process and various consumption quotas can be clearly expressed in quantity. Ansteel Dagushan Mineral Processing Plant originally had 15 ф2.7×2.1m ball mill series, with a designed annual raw ore processing capacity of 3.6 million tons. The concentrate grade increased from 63.71% in 1976 to 66.40% in 1978 by adding fine screens. Achieved by new grinding process. The fine screen regrinding workshop was built at the end of 1977; the investment was 36,075 yuan. After the fine screening and regrinding workshop was put into operation, the grade of the concentrate increased by 2.69% compared with the original process, and the corresponding changes in the consumption quotas and processing costs of the mineral processing were calculated (calculated based on the constant prices in 1980). The grade of the raw ore of the plant in 1976 was 31.93%, and the grade of concentrate The ore grade is 63.71%, the tailings grade is 10.63%, and the beneficiation ratio is 2.492t/t. 3.6 million tons of raw ore can produce 1.44 million tons of concentrate. When the ball mill capacity of the ore dressing plant and the recovery rate of the beneficiation metal do not change, per ton The concentrate ore dressing and processing fee increased by 154.75÷144=1.07 yuan. Here, only the added cost of the regrinding workshop is calculated, but the change in the fixed cost of the original sorting process processing cost shared per ton of concentrate is not calculated when the sorting index changes. B Mathematical statistics method The selection process is basically fixed. As the grade of concentrate gradually increases and various consumption indicators cannot be strictly distinguished, mathematical statistics methods can be used to determine the relationship between the changes in mineral processing costs with grade. The statistical results of the monthly concentrate grades of Dashihe Ore Concentrator from 1977 to 1979 and the ore processing fee after adjustment at the same price level are as follows (the process is omitted): y=-51.21+0.99x (y represents the ore processing fee per ton of concentrate) fee, x represents the concentrate grade) That is, if the concentrate grade increases by 1%, the processing fee for concentrate ore processing will increase by 0.99 yuan per ton. This statistical result does not include the corporate management fee of the mining company. According to statistics from 1978 to 1980, this fee averaged 5.72 million yuan per year (including the water plant and the Dashihe dressing plant). The calculation was based on the average distribution of the two Dashihe dressing plants. RMB 2.86 million should be allocated.