Donganshan beneficiation plant in 1978 March 22 to March 29 were tested to improve concentrate grade of No. 7 system. According to the test results, when the output is basically unchanged at the ball mill stand, Figure 3 shows the following equation for the relationship between the tailings grade and the concentrate grade:
θ=993.987-31.721β+0.2561β ² (4)
The test results show that the tailings grade increases with the increase of concentrate grade. When the concentrate grade changes below 63%, the tailing grade has a relatively small increase; but when the concentrate grade exceeds 63%, the tailing grade is significant. increase.

According to the product quality of the Jiugang Concentrator in 1979, nearly 3,000 data were collected from 939 classes in the dispatch daily report.
The image of the data is shown in Figure 4 as:
y=2.78-1.66x ₁ +0.148x ₂ (5)
Jiuquan Steel 1979 data show that with the increase metal recoveries and improve the ore grade; concentrate grade with increased and improved. This indicates that the ore dressing depth is not enough under the conditions at that time. With the fine grinding of the ore, the minerals and gangues can be better separated, and the purpose of improving the ore recovery rate is increased while improving the concentrate grade.
For most domestic concentrators, as the grade of concentrates increases, the metal recovery rate will be affected. Especially in the process of constant ore and over-grinding, the pure pursuit of high grade has a greater impact on the recovery rate. Figure 4.

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2. Increasing the influence of concentrate grade on the capacity of the ball mill of the beneficiation plant. The mill capacity is reduced. On the one hand, the concentrate production is reduced and the concentrate cost is increased. On the other hand, the ore dressing plant needs to be expanded to compensate for the disappearance of capacity. Occupied investment increased. Therefore, the mill capacity index is one of the important indicators that affect the investment effect of the concentrator.
The capacity of the ball mills in each plant varies with the grade of the ore dressing, and has a lot to do with the nature of the ore and the means to improve the grade of the concentrate. In the beneficiation process is basically fixed, the ore has been ground to a certain size, and then by fine grinding measures to improve the concentrate grade, the ball mill capacity will inevitably decrease. If the grade is improved on the basis of continuous improvement and improvement of the process, the capacity of the ball mill may not be reduced, or even increased to varying degrees.
Before the fine sieving, Nanfen Concentrator used to reduce the grinding grain size to improve the quality of iron concentrate. However, due to the different ore properties, the ore grindability varies greatly, although at the same grinding particle size, the useful dissociation degree of useful minerals and gangue minerals is different, and only most of the mineral monomers can be dissociated. Therefore, it is inevitable that a small amount of continuous organisms and over-pulverized minerals are present in the grinding products, which affects the improvement of the concentrate grade. In order to obtain high-grade concentrates, it is necessary to reduce the grinding capacity, improve the grinding size, reduce the number of continuous organisms, and fully dissociate useful minerals and gangue. The higher the grade requirement for concentrate, the finer the grinding particle size requirements, and the more severe the over-grinding phenomenon. For example, the concentrate grade increased from 65.13% in July-December 1976 to 66.35% in July 1977 to June 1978, and the ball mill processing capacity decreased from 62.48t/(台•h) to 53.40t/(台•h). ), decreased by 9.08t / (Tai • h). Figure 5.

In July, November, 1978 and May 1979, the fine screen self-circulating and re-grinding process was implemented in the third, fourth and second workshops. The second stage fine screen was installed, the sieve hole was 0.2mm, the inclination angle was 56°, and the transformation cost was 800,000. yuan.
The situation after the vibrating fine screen is put into production is very different. The fine sieve will separate the iron concentrate smaller than the separated particle size, and the large dry separation particle size and its continuum become the sieve product and then re-grind and re-select, thereby avoiding and reducing the magnetite over-grinding phenomenon and shortening the grinding. Time has increased the ability of the mill. [next]
The capacity of the ball mill in the Dashihe Concentrator from 1977 to the first quarter of 1981 varied with the grade of the concentrate. Based on this, regression analysis was carried out. Their relationship is:
y=325.66-3.78x (6)
(where y represents the capacity of the ball mill, and x represents the concentrate grade)
That is, the grade of the concentrate is increased by 1%, and the capacity of the ball mill is reduced by 3.78t. The statistical results are shown in Figure 6.

After the fine screening and re-grinding workshop of the Dagushan Concentrator was put into operation, the ball mill capacity was basically maintained at the level of the original process when the concentrate grade was 66%. However, when the concentrate grade is increased again, the mill capacity is reduced. When the concentrate grade reaches 67%, the mill capacity drops more, from 30t/(台•h) to 26t/(台•h). According to the indicators from May 1978 to March 1979, the mill changed the mill capacity according to different grades.
(III) Increasing the cost of concentrates The cost of concentrates includes raw material costs and processing fees. The selected grades of ore are increased, and raw material costs and processing fees are increased. The raw material fee refers to the raw ore cost to be processed per ton of concentrate. Even if other sorting indicators are not affected, the raw ore is increased per ton of concentrate due to the decrease in the yield of the concentrate. increase. The higher the mining cost of the ore, the greater the impact on the beneficiation. When the concentrate grade increases and the recovery rate of the ore dressing metal decreases, the value of the increase in raw material costs is even greater. Therefore, the increase in the cost of raw materials by the concentrate grade depends not only on the changes in the concentrate grade and recovery rate of the ore dressing plant, but also on the cost of the original ore mined by the mine.
The processing cost of iron concentrate includes steel ball, lining board, water, electricity and other materials consumption and power consumption costs, depreciation of fixed assets, repair and maintenance costs, production workers' wages and surcharges, and workshop expenses and business management fees. Wait. These changes in costs can be clearly reflected in the major changes in the process of the concentrator, but in daily production, when the process and equipment are basically unchanged, only some individual selection indicators will change within a limited range. Obvious. In particular, the prices of various consumable materials are constantly changing, and the measurement of the scale of consumption on the site is not allowed, which makes the relationship between the financial statements and the technical indicators not regular. However, whether it is easy to select ore or difficult to select ore, no matter what means to improve the grade of concentrate, the processing cost will always increase with the increase of concentrate grade.
The effect of ore selection on the processing cost of mineral processing can be calculated by the following method.
A Quota calculation method This method is applicable to the process with a large change, and the various consumption quotas can be clearly expressed in quantity.
The original 15 ф2.7×2.1m ball mill series of Dagangshan Concentrator in Anshan Iron and Steel Co., Ltd. designed the annual processing capacity of 3.6 million tons. The concentrate grade increased from 63.71% in 1976 to 66.40% in 1978 by adding fine sieve. Grinding the new process to achieve. The fine screening and regrind workshop was completed at the end of 1977; the investment was 36075 yuan.
After the fine screening and re-grinding workshop was put into production, the concentrate grade was increased by 2.69% compared with the original process, and the corresponding consumption quota and processing cost of the ore dressing were calculated (calculated according to the 1980 constant price).
In 1976, the original ore grade of the plant was 31.93%, the concentrate grade was 63.71%, the tailings grade was 10.63%, the beneficiation ratio was 2.492t/t, and the 3.6 million tons of ore was able to produce 1.44 million tons of concentrate. The capacity of the ball mill in the concentrator and the ore dressing metal When the recovery rate does not change, the processing cost per ton of concentrate ore is increased by 154.75÷144=1.07 yuan. Here, only the increase in the cost of the regrind workshop is calculated, and the change in the fixed cost of the original sorting process processing cost per ton of concentrate is not calculated when the change index is changed.
B Mathematical Statistics When the selection process is basically fixed, as the grades of concentrates are gradually improved and the consumption indicators cannot be strictly distinguished, mathematical statistics can be used to determine the relationship between the processing cost of mineral processing and the grade.
The statistics of the concentrate grades of the Dashihe Concentrator from 1977 to 1979 and the ore processing fees adjusted according to the same price level are as follows (the process is omitted):
y=-51.21+0.99x
(y represents the processing cost per ton of concentrate ore, x represents the grade of concentrate)
That is, the concentrate grade is increased by 1%, and the processing cost per ton of concentrate ore is increased by 0.99 yuan. This statistical result does not include the enterprise management fee of the mining company. According to the statistical average of 5.72 million yuan per year from 1978 to 1980 (including the two plants of the water plant and the Dashi River), the Dashi River plant is calculated according to the average distribution of the two companies. A total of 2.86 million yuan should be allocated.

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